Getting confusing messages on how to measure flame rectifiction is working, some say measure the voltage appox 20v dc others say measure the current in series getting 4 milliamps which is right, 
how to measure flame sense on ioinisation probe is working
- Thread starter corgigazza
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Flame sensing works by passing a small AC Milliamp current down to spark probe which is then rectified by the flame when it lights which is in turn picked up either by the earth of the appliance or a n other probe as DC milliamps.
Therefore who ever told you to test in series on milliamp scale
is the clever chappie you need to be listening to.
Whoever told you it had 20 volts on it was missing the whole principle of flame rectification.
Stan
Therefore who ever told you to test in series on milliamp scale
is the clever chappie you need to be listening to.Whoever told you it had 20 volts on it was missing the whole principle of flame rectification.
Stan
The 20V could refer to a switched live on a pcb after flame rec. has been proven.
The last time I measured the flame sense current itself it was in nano amps.
As stated, check the MI's or call manufs helpline.
The last time I measured the flame sense current itself it was in nano amps.
As stated, check the MI's or call manufs helpline.
Aye that'll be the one 
Milli Micro or nano Its all exactly the same but different, depending on where the decimal point is.
10^-3 = milli
10^-6 = micro
10^-9 = nano
10^-12 = pico
10^-15 = femto
Milli Micro or nano Its all exactly the same but different, depending on where the decimal point is.
10^-3 = milli
10^-6 = micro
10^-9 = nano
10^-12 = pico
10^-15 = femto
Some of you are getting a little confused here.
Flame detection can either be from the same electrode as the spark or a seperate electrode.
Normally a 50 hz voltage is applied derived from the mains. The source impedance is very high usually several megohms. Its often 20-200 vac. It creates a slight out of balance current in the supply and can cause RCDs to trip if there is already significant leakage.
When its being rectified it will give a DC offset voltage and that can usually be measured with a high impedance voltmeter. Alternatively if its a seperate electrode then a DC current can be measured but thats only likely to be about 100uA but varies widely. More relevant is the minimum the circuit will accept as a valid flame check.
There is normally no purpose served by measurements on the flame detection electrode. However if it makes you feel better then you can make measurements on a few boilers of the types you see regularly.
Tony
Flame detection can either be from the same electrode as the spark or a seperate electrode.
Normally a 50 hz voltage is applied derived from the mains. The source impedance is very high usually several megohms. Its often 20-200 vac. It creates a slight out of balance current in the supply and can cause RCDs to trip if there is already significant leakage.
When its being rectified it will give a DC offset voltage and that can usually be measured with a high impedance voltmeter. Alternatively if its a seperate electrode then a DC current can be measured but thats only likely to be about 100uA but varies widely. More relevant is the minimum the circuit will accept as a valid flame check.
There is normally no purpose served by measurements on the flame detection electrode. However if it makes you feel better then you can make measurements on a few boilers of the types you see regularly.
Tony
rob884 said:
As I found out recently reverse polarity can simulate a flame sensing problem. Boiler in question was a Glow worm compact 100 and required current was 1µA
I think they all fail on reverse polarity.
I love reverse polarity it's such a laugh, catches out the cowboys.
Had a great one not long ago, "I think the boiler is quite new, but now it's broken". Yer right, only recently developed a disliking for reverse polarity has it?
I love reverse polarity it's such a laugh, catches out the cowboys.
Had a great one not long ago, "I think the boiler is quite new, but now it's broken". Yer right, only recently developed a disliking for reverse polarity has it?
No !
About 1996 some manufacturers started adding a reverse polarity requirement and by 2002 most had it.
Now it seems to be going out of fashion and some are dropping it.
Perhaps it results in too many calls to the Tech help? Its difficult to see any problem in normal use. Any servicing engineers should always check it first AND recheck when the power is isolated again.
Tony
About 1996 some manufacturers started adding a reverse polarity requirement and by 2002 most had it.
Now it seems to be going out of fashion and some are dropping it.
Perhaps it results in too many calls to the Tech help? Its difficult to see any problem in normal use. Any servicing engineers should always check it first AND recheck when the power is isolated again.
Tony
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I would agree with that statement Paul until I went to service a Potterton Profile which at the time was probably 6 years old.Paul Barker said:
Bearing in mind it was working when I arrived by the time I had serviced it it wasnt rectifying which I thought odd.
Checked all connections and for continuity on the spark lead and probe.
Cust had not had any electrical works done.
Next check was a last ditch but I thought, better check before I order anything. Traced reverse polarity to back of fused spur which had been untouched since the boiler had been put in!
It does happen. Well alright then only once
Stan
I had am amusing visit to a lady who had bought a flat with a two year old boiler.
Her electrician father had rewired the flat and after his rewire the boiler no longer worked. He was adament he had done it correctly!
It turned out the original spur was wrong and the boiler fitter had realised but did the minimum to get the boiler working by reversing the boiler connections.
A nice simple job for me! A little expensive for the daughter!
Tony
Her electrician father had rewired the flat and after his rewire the boiler no longer worked. He was adament he had done it correctly!
It turned out the original spur was wrong and the boiler fitter had realised but did the minimum to get the boiler working by reversing the boiler connections.
A nice simple job for me! A little expensive for the daughter!
Tony
Clearly her father didn't use CRIPER when checking his work. C.ontinuity R.ing I.nsulation resistance P.OLARITY E.arth loop impedance R.CD. Then functional tests.
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